The present invention relates to internal combustion reciprocating engines, especially, but not exclusively, large size 2- and 4-stroke Diesel engines, and relates particularly to cylinder liners for such engines.
More specifically, the invention is concerned with cylinder liners of the type having a neck extending between the cylinder block and the cylinder head of the engine and a number of internal cooling ducts provided in the neck for the through flow of a cooling liquid which in use of the liner enters these ducts from an annular space surrounding the part of the cylinder liner located within the cylinder block and which emerges from the said ducts into a collection chamber which surrounds the neck and from which the cooling liquid is directed towards the cylinder head.
As known, the function of the cylinder liner is to delimit, together with the cylinder head and the crown of the associated piston, the combustion chamber of the cylinder. In this combustion chamber the material of the cylinder liner, and in particular that of its neck enclosed between the cylinder block and the cylinder head of the engine, must be resistant to the high stresses, both thermal and mechanical, resulting from the temperature and pressure of the combustion gases. The possibility of resisting such stresses is dependent, among other factors, upon the means used to limit the operating temperature of the internal wall of the cylinder liner.
The object of this invention is to provide a cylinder liner having an efficient cooling means without this causing any substantial reduction in the strength of the cylinder liner in the neck region enclosed in use of the liner between the cylinder heads and the cylinder block.
A known method of limiting the temperature of the internal wall of cylinder liners in engines, especially large size 2 and 4-stroke Diesel engines, is to provide intensive cooling by means of a series of through ducts, formed by drillings in the neck of the cylinder liner, which are either independent of each other or interconnected, so that the parts which suffer the most severe thermal stress can be traversed by a cooling liquid flowing through the ducts.
In a traditional cylinder liner with an internally cooled neck of the aforementioned type the coolant circulation ducts pass through the neck region of the liner disposed, in use of the liner, between the cylinder block and the cylinder head, thus constituting a dangerous weakness in a relatively highly stressed part of the liner.
The problem with which the present invention is concerned is that of providing a cylinder liner with internal cooling ducts in the region of its neck without substantially weakening the liner by the presence of these ducts.